Oscillating gear



.Patented May 22, 1951 UNITED STATES-PATENT OFFICE OSCILLATING GEAR Joseph D. Kreis, Cleveland, Ohio Application May 7, 1946, Serial No. 667,965

21 Claims. 1

This invention is directed to mechanism for converting continuous rotary motion to Oscillatory motion.

Devices for converting rotary to oscillatory motion have been provided hitherto, and have found many applications. The present invention contemplates the performance of this conversion by a novel mechanism, having advantages of wide applicability, simplicity, and efficiency. The invention. moreover, may provide either an equalacting or a quick-return oscillation; and in either case may superimpose a constant rotation or creep upon the oscillatory movement.

An object of the invention is the provision of mechanism to convert rotary motion to oscillating motion.

Another object of the invention is the provision of mechanism to convert rotary motion to oscillating motion of equal velocity in each direction.

Another object of the invention is the provision of mechanism to convert rotary motion to oscillating motion of unequal velocity in the two directions.

Another object of the invention is the provision of mechanism to convert rotary motion to oscillating motion and to provide an additional constant rotary motion or creep.

A further object is the provision of such mechanism employing simple easily fabricated parts.

A further object is the provision of such mechanism having high efliciency, w accelerations of parts, and low stresses.

A still further obfect is the provision of such mechanism which may readily be adapted for different requirements as to amplitude and frequency of oscillations, creep rate, and input speed.

Other objects and advantages more or less ancillary to the foregoing and the manner in which all the various objects are realized will appear in the following description, which, considered in connection with the accompanying drawings, sets forth the preferred embodiment of the invention.

Referring to the drawings:

Fig. 1 is an elevation of a form of gearing according to the invention.

Fig. 2 is a plan view of the same;

Fig. 3 is an exploded view in perspective of the same; and Fig. 4 is an elevation of a second form of gearing according to the invention.

The preferred embodiment of the invention, as may be seen from Figs. 1 to 3, resembles in some respects the common compound planetary gearing, employed in speed reducing gear and the like;

and the invention is based in part upon the principles of such gearing.

The gearing of Figs. 1 to 3, which is adapted to produce equal velocity in both directions of movement, comprises two sun gears H and I2, fixed on coaxial shaftsl3 and It, the shaft l3 being restrained against rotation by the anchorage indicated schematically at l5. The shaft M is the output shaft, which may be connected to a driven device (not shown) of any desired type. A yoke I6 is mounted for free rotation upon the shafts l3 and I4, and is preferably formed of two shallow U-shaped sections I? and I8 to permit assembly of the gearing, the sections being joined by rivets I9 and 20.

A gear 2! journalled on the shaft I3 and secured to the yoke it, as by machine screws 22, receives the constant rotational input of the mechanism. Two planet gears 23 and 24, meshing with the sun gears l l and I2, respectively, are mounted in the yoke 15. The gear 23 is formed with a concentric shaft.25 on one face thereof which is journalled in the yoke element [1. The opposed face of the gear is machined to form a diametral rib or key 26 of rectangular cross section.

An Oldham coupling disk 21 is interposed between the gears 23 and 24. The disk is formed with a diametral groove 28 in one face thereof, and a similar diametral groove 29 in the opposite face, in quadrature with the groove 28. The rib 26 is engaged for sliding movement in the groove 28 and a diametral rib 30 on the inner face of the planet gear 24 is slidably engaged in the groove 29. The faces of the disk 2! are in contact with the inner faces of the planet gears.

It will be seen that as the input gear 2| is driven, the yoke will revolve about the shafts l3 and I 4, thus causing the planet gear 23 to roll around the gear I I, and the planet gear 24, under the action of the Oldham coupling, to roll around the gear I2.

The planet gear 24 is provided with an eccentric shaft 3| disposed in its outer face, which is received and guided in a slot 32 in the yoke element l8, the slot permitting translation of the shaft only in a radial direction with respect to the shafts l3 and Hi. In order to maintain gears I 2 and 24 in mesh, a freely swinging link 34 is provided, having a bearing 36 at one end on the shaft It, and a bearing 38 at the other end in which is journalled a drum 40 integral with the planet gear 24, and concentric therewith. The link 34! slides against the inner face of yoke member 18 as the eccentric planet gear rotates, per- 3 mitting the shaft 3| to slide in the slot 32, and retaining the planet gear in proper mesh with its sun gear.

To analyze the operation of the gear, let it be assumed that the two sun gears are of equal size and the two planet gears are also of equal size. Then assume the yoke remains stationary, and the lower sun gear rotates clockwise, as viewed from above, at constant speed. Its planet will rotate counter-clockwise at a constant speed and at a rate determined by the ratio of the two gears. The eccentric planet gear 24 will rotate counter-clockwise at the same constant rate as planet 23. Its shaft 3! will reciprocate in the slot 32, and the center of the gear will oscillate in an arc of a radius determined by the length of its link 34 and of orbital magnitude determined by the eccentricity of the shaft 3!.

The motion of the planet gear 24 will be communicated to the sun gear !2 and output shaft 14. The output motion may be regarded as having two components: First. a constant clockwise rotation equal to that of the lower sun gear, transmitted to it by the constant rotation of the planet gear 24 relative to the yoke. Second, an oscillating motion caused by the swinging (trans-- lation) of the planet gear on the link 34 as the eccentric shaft 3| transverses the slot. The second component is caused solely by translation of the gear 24, as its rotation has been accounted for in the first component.

It is clear that if the shaft 53 is held stationary, and the input gear 2| and yoke i6 are rotated, the motion of the output shaft l4, relative to the shaft 13 will be the same as under the previous conditions. It follows that the constant rotational component of the output is zero, since shaft I3 is stationary, and that only the oscillating component of the output will remain.

The output motion may be more specifically defined mathematically. If R equals the ratio of the pitch radius of the sun gears to the pitch radius of the planet gears, and Q equals the ratio of the eccentricity of the planet gear shaft to the sum of the pitch radii of the sun and planet gears. X represents rotation of the input, and Y rotation of the output, then the angles being taken as zero when the eccentric shaft is in its innermost position. From this it can be seen that the frequency of oscillation equals R, times the input speed, and that the amplitude (half of the total swing) of the oscillations will equal arcsin (Q sin RX) arcsin Q 'the gear I l.

where R1 and R2 are the ratios of sun gear pitch diameter to planet gear pitch diameter for the first (concentric) and second (eccentric) sets of gears, respectively. The total output movement,

the frequency being determined by the concentric set of gears and the amplitude by the eccentric set.

It will be apparent that in a gear arrangement as illustrated in Fig. 1, the upper shaft 14 could be fixed and the lower shaft l3 could be the output shaft. This constitutes a simple inversion of the apparatus, with the eccentric planet gear rolling on the fixed sun gear, and the concentric planet gear driving the output sun gear. In this case, the oscillating motion is quick-return; that is, the stroke in one direction requires less time than that in the other. The amplitude and frequency of the oscillations depends solely upon the gear ratios, the eccentricity of the planet gear shaft, and the input speed, and are the same whether the first or the second planet gear is eccentric. When the first planet gear is eccentric, the relative times required for the forward and return strokes are determined as follows: Letting 360 represent the entire cycle (both strokes), the quicker stroke occupies l'-2(1+R) arcsin Q and the slower stroke occupies 180+2(1+R) arcsin Q where R and Q are defined as before.

Fig. 4 illustrates a modified form of gear in which both planet gears are eccentric, it being otherwise similar to the form previously described.

The planet gear 23 has an eccentric shaft 25 received in a radial slot M in the yoke member 17. A link 33, having a bearing 35 on the shaft i 3 and a bearing 37 for the concentric journal 39 of the gear 23 retains the gear 23 in mesh with Otherwise, the structure is identical to that of Fig. 1.

The eccentric shafts of the planet gears are oppositely disposed with respect to the gear centers, this relationship being maintained by the Oldham coupling.

With two eccentric gears,a greater amplitude of oscillation may be generated than with one, and, with this construction, the quick-return operation is inherent. The mathematical analysis of the double eccentric gear becomes rather involved for a general case. values of the constants, it involves merely the application of well-known kinematic principles. A creep may be introduced in the output of the double eccentric gearing by making the gear ratios unequal, just as in the other forms. For a given eccentricity of the planet gears, the amplitude of oscillating motion is double that with a single eccentric gear.

In the appended claims, the term circular gear and reference to circular gears are used for conciseness to recite gears in which the pitch line is a circle. The term "eccentric gear and reference to gears that are eccentric are used to recite a circular gear as defined above rotating about an axis or shaft which is offset from the s ats? of the P tch c rcle.

For any specific I Reference in the claims to a concentric'gear is used to recite a gear in which the axis of rotation of the gear is at the center of the pitch line.

I claim:

1. An oscillating gear mechanism comprising two coaxial sun gears, a yoke rotatable about the axis of the sun gears, two planet gears on the yoke, one meshed with each sun gear, means coupling the planet gears for equal rotation, and means for causing one planet gear to be oscillated about the axis relative to the yoke.

2. An oscillating gear mechanism comprising two coaxial sun gears, a yoke rotatable about the axis of the sun gears, two planet gears on the yoke, one meshed with each sun gear, means coupling the planet gears for equal rotation, and means for causing the planet gears to be oscillated about the axis relative to the yoke.

3. An oscillating gear mechanism comprising two coaxial sun gears, a yoke rotatable about the axis of the sun gears, two planet gears on the yoke, one meshed with each sun gear, means couplnig the planet gears for equal rotation, and means actuated by rotation of a planet gear for causing one planet gear to be oscillated about the axis relative to the yoke.

4. An oscillating gear mechanism comprising a stationary gear, a planet gear, having a concentric shaft, rolling around the stationary gear, a gear having an eccentric shaft, means. coupling the shafts of the planet gear and eccentric gear for equal angular movement about the stationary gear, means coupling the planet gear and. eccentric gear for equal angular movement about their shafts, and a fourth gear around which the eccentric gear rolls, the fourth gear being circular and concentric.

5. An oscillating and creeping gear mechanism comprising a stationary gear, a planet gear rolling around the stationary gear, a gear having an eccentric shaft, means coupling the shafts of the planet gear and eccentric gear for equal angular movement about the stationary gear, means coupling the planet gear and eccentric gear for equal angular movement about their shafts, and a fourth concentric gear around which the eccentric gear rolls, the ratio of the stationary gear to the planet gear being different from the ratio of the fourth gear to the eccentric gear.

6. An oscillating gear mechanism comprising two collinear shafts, a sun gear on each shaft, a yoke rotatable about the shafts, two planet gears mounted on the yoke for rotation relative thereto, one planet gear meshing with each sun gear, and coupling means constraining the planet gears to concurrent rotation, one of the gears being eccentric meshing with a concentric gear.

7. An oscillating gear mechanism comprising two collinear shafts, a sun gear on each shaft, a yoke rotatable about the shafts, two planet gears mounted on the yoke for rotation relative thereto, one planet gear meshing with each sun gear, and coupling means constraining the planet gears to concurrent rotation, one of the planet gears being eccentric and meshing with a concentric sun gear.

8. An oscillating and creeping gear mechanism comprising two collinear shafts, a sun gear on each shaft, a yoke rotatable about the shafts, two planet gears mounted on the yoke for rotation relative thereto, one planet gear meshing with each sun gear, and coupling means constraining the planet gears to concurrent rotation, one of the gears being eccentric meshing with a con- 61 centric gear, and the ratios of the meshing gear pairs being unequal.

it. An oscillating gear mechanism comprising two coaxial sun gears, one of the sun gears being fixed, a yoke rotatable about the axis of the sun gears, two planet gears, means for retaining each planet gearin mesh with a sun gear, an eccentric shaft for each planet gear, means constraining the eccentric shafts to concurrent angular rotation with the yoke, and means constraining the planet gears to concurrent rotation about their shafts.

- 10. An oscillating gear mechanism comprising two coaxial sun gears, one of the sun gears being fixed, a yoke rotatable about the axis of the sun gears", two planet gears, means for retaining each planet gear in mesh with a sun gear, a shaft for each planet gear, one of the shafts being eccentric, means constraining the shafts to concurrent angular rotation with the yoke, and. means constraining the planet gears to concurrent rotation about their shafts.

11. An oscillating gear mechanism comprising two collinear shafts, a sun gear fixed on each shaft, two planet gears, one meshing with each sun gear, a journal concentric with each ear, means for maintaining a constant distance between the journals of each meshing pair of gears, a shaft for each planet gear, a yoke rotatable about the axis of the collinear shafts, means constraining the planet gear shafts to rotation about the axis with the yoke, and means coupling the planet gears to enforce equal rotation of the planet gears, at least one of the gears being eccentric.

12. An oscillating gear mechanism comprising two collinear shafts, a sun gear fixed on each shaft, two planet gears, one meshing with each sun gear, a journal concentric with each gear, means for maintaining a constant distance between the journals of each meshing pair of gears, a shaft for each planet gear, a yoke rotatable about the axis of the collinear shafts, means constraining the planet gear shafts to rotation about the axis with the yoke, and means-coupling the planet gears to enforce equal rotation of the planet gears, at least one of said planet gears being eccentric.

13. An oscillating gear mechanism comprising two collinear shafts, a sun gear fixed on each shaft, two planet gears, one meshing with each sun gear, a journal concentric with each gear, means for maintaining a constant distance between the journals of each meshing pair of gears, a shaft for each planet gear, a yoke rotatable about the axis of the collinear shafts, means constraining the planet gear shafts to rotation about the axis with the yoke, and means coupling the planet gears to enforce equal rotation of the planet gears, said planet gears being eccentric.

14. An oscillating gear mechanism comprising two coaxial sun gears, a yoke rotatable about the axis of the sun gears, two planet gears on the yoke, one meshed with each sun gear, means coupling the planet gears for equal rotation, and means actuated by rotation of the yoke for causing one planet gear tobe oscillated about the axis relative to the yoke.

15. An oscillating gear mechanism comprising two sun gears, a planet gear meshing with each sun gear, and means coupling the planet gears for concurrent rotation, one of the gears being eccentric and circular, and the ratios of the sun gears to their respective planet gears being unequal.

16. An oscillating planetary gear mechanism comprising two coaxial sun gears, a yoke rotatable about the axis of the sun gears, two planet gears mounted in the yoke and meshing with the sun gears, respectively, and means coupling the planet gears for joint rotation, each planet gear being mounted on an axis of rotation supported by the yoke, the center of one planet gear being displaced from the said axis of rotation of the said one planet gear, and the other abovementioned gears being concentric.

1'7. An oscillating planetary gear mechanism comprising two coaxial and concentric sun gears, a yoke rotatable about the axis of the sun gears,

two planet gears mounted in the yoke and mesh- :ing with the sun gears, respectively, and means coupling the planet gears for joint rotation, each planet gear being mounted on an axis of rotation supported by the yoke, the center of each planet gear being displaced from the said axis of rotation of the said planet gear.

18. An oscillating planetary gear mechanism comprising a fixed sun gear, a rotatable sun gear coaxial with the fixed sun gear, a yoke rotatable about the axis of the sun gears, two planet gears mounted in the yoke meshing with the sun gears, respectively, and means coupling the planet gears for concurrent rotation, each planet gear being rotatable about an axis therefor mounted in the yoke, one planet gear having a center and the said center being displaced from the said yoke-mounted axis of rotation of the said planet gear, all the said gears having circular pitch lines.

19. An oscillating planetary gear mechanism comprising a fixed sun gear, a rotatable sun gear coaxial with the fixed sun gear, a yoke rotatable about the axis of the sun gears, two planet gears mounted in the yoke meshing with the sun gears, respectively, and means coupling the planet gears for concurrent rotation, each planet gear being rotatable about an axis therefor mounted in the yoke, the planet gear meshing with the fixed sun gear having a center and the said center being displaced from the said yoke-mounted axis of rotation of the said planet gear, the fixed sun gear being concentric with the axis of rotation of the yoke.

20. An oscillating planetary gear mechanism comprising a fixed sun gear, a rotatable sun gear coaxial with the fixed sun gear, a yoke rotatable about the axis of the sun gears, two planet gears mounted in the yoke meshing with the sun gears, respectively, and means coupling the planet gears for concurrent rotation, each planet gear being rotatable about an axis therefor mounted in the yoke, the planet gear meshing with the rotatable sun gear having a center and the said center being displaced from the said yoke-mounted axis of rotation of the said planet gear, the rotatable sun gear being concentric with the axis of rotation of the yoke.

21. An oscillating planetary gear mechanism comprising two coaxial sun gears, a yoke rotatable about the axis of the sun gears, two planet gears mounted in the yoke and meshing with the sun gears, respectively, and means coupling the planet gears for joint rotation, each planet gear being mounted on an axis of rotation supported by the yoke, one of the gear pairs consisting of a said sun gear and a said planet gear meshing therewith consisting of a concentric gear and an eccentric gear.

JOSEPH D. KREIS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,948,095 Boynton Feb. 20, 1934 2,296,892 Andrew Sept. 29, 1942 2,312,376 Andrew Mar. 2, 1943 

